diff --git a/crc16.py b/crc16.py
index f3d1777..ade6f26 100644
--- a/crc16.py
+++ b/crc16.py
@@ -90,24 +90,34 @@ def encode(in_data):
     M = [0] * 16 + data_binary
     L = [0] * (len(data_binary)) + [1] * 16
     G = [1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1]
-    FCS_poly = Polynomial.divide(Polynomial.add(Polynomial(M), Polynomial(L)), Polynomial(G))
-    FCS = FCS_poly.coefficients + [0] * (16 - len(FCS_poly.coefficients))
+    result_poly = Polynomial.divide(Polynomial.add(Polynomial(M), Polynomial(L)), Polynomial(G))
+    result = result_poly.coefficients + [0] * (16 - len(result_poly.coefficients))
 
-    FCS.reverse()
+    result.reverse()
     data_binary.reverse()
-    data_binary = data_binary + FCS
+    data_binary = data_binary + result
     data_binary = [data_binary[i:i+8] for i in range(0, len(data_binary), 8)]
-    data = [chr(int(''.join(map(str, byte)), 2)) for byte in data_binary]
+    data_binary = [int(''.join(map(str, byte)), 2) for byte in data_binary]
 
-    return ''.join(data)
+    fcs = [hex(byte) for byte in data_binary]
+    fcs = fcs[-2:]
+
+    data = [chr(byte) for byte in data_binary]
+    data = ''.join(data[0:-2])
+
+    return data, fcs
 
 
-def check_fcs(in_data):
+def check_fcs(in_data, fcs):
     data = in_data
     data = list(data)
     data_binary = [bin(ord(char)).replace('b', '') for char in data]
     data_binary = [normalize_byte(byte) for byte in data_binary]
     data_binary = [int(bit) for bit in list(''.join(data_binary))]
+    fcs_binary = [bin(int(in_hex, 16)).replace('b', '') for in_hex in fcs]
+    fcs_binary = [normalize_byte(byte) for byte in fcs_binary]
+    fcs_binary = [int(bit) for bit in list(''.join(fcs_binary))]
+    data_binary += fcs_binary
     data_binary.reverse()
 
     C = [0] * 16 + data_binary
@@ -124,15 +134,17 @@ def check_fcs(in_data):
 def main():
     try:
         if sys.argv[1] == '-e' or sys.argv[1] == '-encode':
-            arg = encode(sys.argv[2])
-            print(arg)
-            print(check_fcs(arg)) # powinno zawsze zwracać true
+            arg, fcs = encode(sys.argv[2])
+            print(arg, fcs)
+            print(check_fcs(arg, fcs)) # powinno zawsze zwracać true
         elif sys.argv[1] == '-c' or sys.argv[1] == '-check':
-            print(check_fcs(sys.argv[2]))
+            arg = sys.argv[2]
+            fcs = ast.literal_eval(sys.argv[3])
+            print(check_fcs(arg, fcs))
         else:
             raise IndexError
     except IndexError:
-        print("To encode: python3 CRC16.py -e [argument]\nTo check FCS: python3 CRC16.py -c [argument]")
+        print("To encode: python3 CRC16.py -e [argument]\nTo check result: python3 CRC16.py -c [argument] [fcs]")
 
 
 if __name__ == "__main__":